Methods and means for parts assembly



Dec. 12, 1967 .1. T. SILER 3,357,730

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PART (6 80 03) 883 W F/QZ FASTENER HOLE LOCATION NORMAL LOCATION OFHOLES INVENTOR Joseph T Si/er ATTOR NFYS Dec. 12, 1967 J. T. SILER3,357,730

METHODS AND MEANS FOR PARTS ASSEMBLY Original Filed Oct. 27, 1961 4Sheets-Sheet 2 LIGHT uem' FORCE FIT FORCE FIT INVENTOR Joseph 7. Si/erATTORNEYS Dec. 12, 1967 J. T. SILER 3,357,730

METHODS AND MEANS FOR PARTS ASSEMBLY Original Filed Oct. 27, 1961 4Sheets-Sheet 1i 9 803813192 9025; w M i i 5/ I I 84 as I 9/ 94 H. may

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INVENTOR Joseph T SIIer Dec. 12, 1967 J. T. SILER 3,

METHODS AND MEANS FOR PARTS ASSEMBLY Original Filed Oct. 27, 1961 4Sheets-Sheet 4 ll l ILI}: /37

l l I 1 i I a! 26 1 r3 3 I A INVENTOR I Joseph I Si/er M kw UnitedStates Patent METHODS AND MEANS FOR PARTS ASSEMBLY Joseph T. Siler, 203%E. Virginia, McKinney, Tex. 75069 Original application Oct. 27, 1961,Ser. No. 148,190, now Patent No. 3,257,720, dated June 28, 1966. Dividedand this application Apr. 29, 1963, Ser. No. 276,560

6 Claims. (Cl. 287189.36)

This invention relates to new and useful improvements in methods andmeans for parts assembly.

This application is a division of my copending application, Ser. No.148,190, filed Oct. 27, 1961, now US. Patent No. 3,257,720 and relatesin certain respects to my copending application Ser. No. 137,166, filedSept. 11, 1961, now U.S. Patent No. 3,158,045, and to my US. Patent No.3,006,443, issued Oct. 31, 1961, and reference is made thereto.

The invention is particularly directed to improved methods and means foralining two or more parts as may be desired and for securing said partstogether in such alined position, and in making provision for suchalinement and the passage of fastening elements through the partswithout misalinement thereof or disturbing of such previously determinedpositions. Thus, in one respect, the invention is concerned with theattaching or securing of one part to another in a precise andpredetermined position, coupled with arrangements allowing the removalof such part and its replacement in such previously determined preciseposition or its replacement by a substantially identical replacement orinterchangeable part Without loss of the precise alinement andpositioning desired.

In fastening together parts an assembly, each of which may be consideredinterchangeable with other substantially identical parts, certainfactors in the detail parts and in their relationship to each other mustbe maintained if a given set of physical characteristics is to exist inthe finished assembly. These factors are:

(1) The physical outline of each detail part must be essentially thesame as every other substantially identical detail part within theallowable tolerances present.

(2) The detail parts must mate together in essentially the same physicallocation in reference to each other in all assemblies and again withinthe allowable mismate tolerance which is present. This is part shift.

(3) Gnce the detail parts have been placed in juxta posed relationshipthe pre-formed fastening holes must be in alinement in order to receivefastening members therethrough.

In certain parts which are classified .interchangeable at attachingpoints only factor (1) above and the physical outline of the part isaltered on assembly to physical compatibility with the physical outlinesof adjacent parts. Complete interchangeability, which involves all threefactors, including factor (1), is considered to be present in thediscussion herein of the improved methods and means, but factor (1) neednot necessarily be present to practice the improved methods and utilizethe improved means.

The invention will be described largely with respect to its utilizationin the assembly of aircraft structures since aircraft assemblies in mostcases involve close tolerances, high loadings or low safety factors,critical limitations as to the placing of and the oversize allowance offastener openings or holes, and other characteristics rendering thepresent invention particularly adaptable to that field. It is to benoted, however, that the invention is equally applicable to all types ofmechanical assemblies where high accuracy of part alinement and locationas well as fastener opening alinement and structural superiority isnecessary and desirable.

3,357,730 Patented Dec. 12, 1967 In carrying out the invention one ormore locator openings or holes are formed in each of the parts to bejoined, and bushings having fastener receiving bores are positioned insaid openings, the locator bushings having their bores formedconcentrically, or possibly with a relatively slight amount ofeccentricity. The locator openings are necessarily positioned with veryexacting accuracy and to relatively small tolerances. One of the locatoropenings or holes should also be designated as a dimensional referencehole, from which the position of all other fastener openings or holesare measured to prevent tolerance build up, and should be positionedwithin the applicable tolerances to provide the desired edge distancesin the parts to be joined, that is, the maintaining of the distances ofthe holes in the two mating parts at this particular fastening locationspaced as equally as possible or as may be desired from the nearestadjacent edges of the two parts. The dimensional reference locator holemay also be located to close tolerances in relation to other physicalpoints of important relativity between the parts joined.

Following the foregoing, the remainder of the fastener holes may belocated with somewhat larger tolerances, and fastener bushings ofgreater eccentricity in respect to their fastener receiving borespositioned therein and adjusted for alinement of said bores.

It is, therefore, a principal of the invention to provide improvedmethods and means for fastening together mating parts with extremeaccuracy of alinement and fastener bore location.

A further object of the invention is to provide improved methods andmeans of the character described in which all necessary adjustments maybe made from one side of the mating parts.

A still further object of the invention is to provide improved methodsand means of the character described by which greater strength may beimparted to a joint without necessarily increasing the strength of thefastening element; and which, in addition, permits the fullest use ofhigh strength fastening elements of minimum size or diameter.

An additional object of the invention is to provide improved methods andmeans for fastening together mating parts through the use of which partshifts between the parts under loads are precluded even though thefastening elements may not have been tightened as fully as desirable orwhen undetected tolerance build ups may have allowed some looseness inthe bushing-hole fit.

is excluded I Another object of the invention is to provide improvedmethods and. means for fastening together mating parts which permit theuse of lighter fastening elements without any sacrifice in strength, andby which a multiplicity of methods of fastener application may becarried out.

A further object of the invention is improved methods and means of thecharacter described with which may be utilized virtually any of theexisting types of selflocking fasteners and/or fasteners designed toensure a predetermined tightening torque.

Yet another object of the invention is to provide improved means forfastening together mating parts which makes provision for increasedjoint strength at the points or planes of greatest stress.

An additional object of the invention is to provide an improved meansfor fastening together mating parts which provides for the use of acounter-sunk bolt without appreciable loss of strength, resulting inreduced projection of the fastener and better clearance in conditions ofreduced clearance with adjacent parts, while simultaneously resulting ina decreased total Weight of the fastening elements.

Stil lanother object of the invention is to provide an improved jointforming method in which one or more locator fastenings are positionedwith great accuracy whereby remaining fastening holes may require lessaccuracy of location.

A construction designed to carry out the invention will be hereinafterdescribed, together with other features of the invention.

The invention will be more readily understood from a a reading of thefollowing specification and by reference to the accompanying drawings,wherein examples of the invention are shown, and wherein:

FIG. 1 is a front elevationnal view of a closure plate illustrating thecarrying out of the methods and means of this invention,

FIG. 2 is a front elevational view, partly broken away illustrating thepart mating with the part illustrated in FIG. 1,

FIG. 3 is a diagrammatic view illustrating the methods of solving theproblem of fastener hole eccentricity or misalinement,

FIG. 4 is a side elevational view of an anchor nut type fastenerconstructed in accordance with this invention, along with the aliningtool,

FIG. 5 is a bottom plan view of the structure of FIG. 4,

FIG. 6 is a vertical, longitudinal, sectional view taken on the line 66of FIG. 5, showing upper flush bushing now alined and in place,

FIG. 7 is a bottom plan view of a modified form of an anchor nutfastener,

FIG. 8 is a vertical, longitiudinal, sectional view taken on the line8-8 of FIG. 7,

FIG- 9 is a top plan view of the form of the invention shown in FIGS. 7and 8,

FIG. 10 is a top plan view of the fastening bolt adapted for utilizationin the forms of the inventions shown in FIGS. 6 and 8,

FIG. 11 is a side elevational view of the fastening bolt of FIG. 10,

FIG. 12 is a top plan view similar to FIG. 9 but showing a concentricform of the anchor nut fastener,

FIG. 13 is a bottom plan view of the fastener of FIG. 12,

FIG. 14- is a vertical, longitudinal, sectional view taken on the line1414 of FIG. 13,

15 is a bottom plan view of another form of the anchor nut fastener inwhich the fastening receiving bore has only slight eccentricity,

FIG. 16 is a vertical, longitudinal, sectional view taken upon the line16-16 of FIG. 15,

* FIG. 17 is a top plan view of a protruding head form of the fasteningbushing adapted to receive a countersunk bolt,

FIG. 18 is a vertical, longitudinal, sectional view taken upon the line18-18 of- FIG. 17,

FIG. 19 is a top plan view of still another modification of theinvention,

FIG. 20 is a vertical, longitudinal, sectional view taken upon the line20- 20 of FIG 19,

FIG. 21 is a bottom plan view of the lower fastener assembly of FIG. 20,

- FIG. 22 is a top plan view of yet another form of the fastener bushingassembly,

FIG. 23 is a vertical, longitudinal, sectional view taken upon the line2323 of FIG. 22,

FIG. 24 is a bottom plan view of the lower fastener assembly of FIG. 23,

FIG. 25 is a plan view of an aircraft type stressed access doorillustrating the utilization of the methods and means of this invention,

FIG. 26 is a vertical, longitudinal, sectional view taken upon the line26-26 of FIG. 25, and

FIG. 27 is a vertical, transverse, sectional view taken upon the line27-27 of FIG. 25.

In carrying out the invention, several different methods may be followedin positioning the holes in the parts for receiving the fasteningmembers and for alining the fastener bushings or locator bushingstherein. One method for attaching mating or juxtaposed parts for fullinterchangeability of the parts utilizes two locator holes in each partaccurately located in relation to each other and preferably located inopposite corners or diagonally or diametrically opposed portions of eachpart. The use of these two accurately positioned locator holes in eachmating part satisfies the requirements of factor (2), listedhereinabove, and permits the requirements of factor (3) to be metthrough the use of locator bushings having only a relatively smallamount of eccentricity. It is also possible to use concentric locatorbushings for these locator holes if the tolerances of the center linelocations of the locator holes are held extremely close and a slightamount of oversize or slop is allowed in the fastenerbushing-and/orbushing-bushing hole fits. The amount of tolerance permissible in regardto mismate of the mating parts (part shift) determines the degree oftolerance fineness necessary for the location of the locator holes.Concentric locator bushings without appreciable oversize in the holesreceiving the bushings or in the holes receiving the fasteners wouldnecessitate tolerances for the location of the center lines of the holesof approximately $00005 inch. No part shift mismatch would bediscernable between the parts. On the other hand, if a part shiftmismatch of 0.010 inch is permissible, locator bushings with 0.005 incheccentricity would be allowable as would tolerances for the center linelocation of the locator holes of $0.007 inch, as will be explainedhereinafter. Since a primary objective of the invention, however, is toreduce the part shift between the mating parts to a practical value nototherwise readily obtainable without tedious and timeconsuming machiningoperations to locate the locator openings to very small' tolerances,somewhat more accurate positioning of the locator holes becomesdesirable.

In order to explain the importance of the tolerances on locator holecenter line location dimensions, and to show why much less exactingtolerances are required to mate two holes rather than three or moreholes, it will be well to state certain basic facts.

(:1) In order to prevent tolerance build up all hole location dimensionsmust be referred to a dimensional reference hole which, as pointed outabove, is desirably one of the locator holes.

(b') It may now be seen that when the dimensional reference holes ineach part are perfectly alined and all location dimensions or fastenerholes are located from the dimensional reference. holes, that themaximum hole misalinement possible is as great with three holes as it iswith any larger number of holes.

(0) In studying the initial mating of the parts at the locator holes itcan now be seen that mating two hole locations requires tolerances whichare only one-half as severe as when three or more hole locations aremated. This is true because the required shift may be absorbed one-halfby each part so that the small amount of shift involved from truealinement will have little effect on the alinement of the remainingholes, and in practical usage is most often taken care of by probabilityfactors unless the initial part shift is inordinately large.

This is illustarted in FIGS. 1 through 3 in which the numeral 30designates an approximately rectangular closure door or plate having inits lower left-hand corner a counterbored locator bushing opening 31very accurately positioned with respect to the edges of the plate 30 asindicated at 32 and 33. Locator hole 31 may also be designated as thedimensional reference hole. Beginning with locator hole 31, theremaining bushing holes in plate 30 have been numbered counterclockwise34 through 44, it being noted that hole 39,- diagonally opposite locatorhole 31 may also be a locator hole, but that only hole 31 functions asthe dimensional reference hole. Thus, as indicated at 45 and 46, hole 43is located with respect to hole 31, hole 36 is also located with respectto hole 31 as indicated at 47, hole 37 is located with respect to hole31 as indicated at 48, and locator hole 39 is positioned with respect tolocator hole 31 as indicated at 49 and 50.

The part 51 which mates with plate 30, and which might be the skin ofthe aircraft or any other member, is shown in FIG. 2 and is providedwith a central access opening 52, which is to be covered or closed bythe plate 30, surrounded by a plurality of bushing openings which may ormay not be counterbored or countersunk from either side of the memberdepending upon the type of bushing to be used. The hole 53 which is toregister with hole 31 and which is both a locator hole and a dimensionalreference hole again is very accurately positioned to close toleranceseither With respect to the edge of the part as indicated at 54 and 55 orwith respect to the margin of the opening 52, or both. It might also :bepositioned with respect to some other point of relative positionalimportance (not shown). The bushing openings in member 5]. are numberedfrom 56 through 66 proceeding counterclockwise from locator hole 53.Again, hole 61 may be a second locator hole and is positioned to closetolerances with respect to hole 53 as indicated at 67 and 68, andlocator hole 61 is, of course, the hole adapted to register or nearlyregister with locator hole 39 in plate 30. The remaining bushingopenings are located with respect to locator hole 53 with somewhatlarger tolerances, as indicated at 69 for hole 58, 70 for hole 59, and71 and 72 for hole 65. For purposes of illustration, a tolerance of$0.002 inch has been permitted for positioning of the second locatorholes 39 and 61, and a tolerance of $0.03 inch for location of theremaining bushing openings. To illustrate the maximum misalinement ofthe bushing openings other than the locator holes which may occur underthe designated tolerance, hole 43 in plate 30 deviates from its correctposition by 0.03 inch both vertically and horizontally, and thecorresponding bushing opening 65 in member 51 correspondingly deviatesthe maximum distance permissible both vertically and horizontally but indirections opposite to hole 43. Thus, a mismatch of 0.06 inch in boththe vertical and horizontal directions occurs between this pair ofholes.

As noted above and as will be discussed more fully hereinafter, eitherconcentric locator bushings may be utilized at one or both of thelocator hole positions in each part, slightly eccentric bushings may beutilized in one or both locator hole positions of each part, or acombination of concentric bushings at one locator position and bushingsof slight eccentricity at another locator position may be used. In theremaining bushing openings, fastener bushings of somewhat greatereccentricity would be employed, and the necessary eccentricity isillustrated diagrammatically in FIG. 3 wherein misalined openings 43 and65 are used as an example. The correct or proper location of the centerlines of the fastening openings is indicated at 73, it being noted thatthe center line of opening 43 having a radius R is off by 0.03 inch bothupwardly and to the right as indicated at 74 and 46, while the centerline of opening 65, of radius R, is off 0.03 inch to the left anddownwardly, as indicated at 72 and 75. Thus, the distance between thecenter lines of the two openings is 0.06 inch. In order to accommodatethis misalinement, a bushing 76 having an eccentric bore 77 ispositioned in hole 43, and a bushing 78 having a similar eccentric boreis positioned in hole 65. The bushings may be rotated in the bushingholes until their bores are exactly alined, as shown in the illustrationin FIG. 3, such adjustment being made half by one bushing and half bythe other, as indicated at 79. The eccentricity of the bores of eachbushing must be at least 0.042 inch if the permissible tolerance inlocation of the bushing openings is $0.03 inch, this amount ofeccentricity being calculated at 0.03 inch times the secant of 45.

Similar locator bushings with either concentric bores or very slightlyeccentric bores may be used in either pair or both pairs of locatorholes 31 and 53, and 39 and 61. Assuming for the locator holes atolerance of $0.002

inch, and following the above illustration, if concentric locatorbushings are used in holes 31 and 53, locator bushings having aneccentricity of a minimum of 0.000 inch may be used in locator holes 39and 61, this figure being obtained by multiplying the tolerance of 0.002inch by the secant of 45. If, however, a part shift of 0.003 inchbetween the plate 30 and the member 51 is permissible, locator bushingshaving an eccentricity of only 0.0015 inch may be employed in all fourlocator holes so that one-half the deviation of locator holes 39 and61rnay be accommodated in the locator bushings therein, and onehalfaccommodated by the locator bushings in the locator holes 31 and 53. Inother words, one-half of the mismatch is assumed in each pair of locatorholes. Conversely, it is possible to use four locator bushings with aneccentricity of 0.0003 inch as originally, and a larger hole locationaltolerance of $0.004 inch in mating the two locator hole positions. Inthis case, however, the permissible part shift must be 0.006 inch. Smallamounts of part shift from true alinement between the plate 30 and themember 51 will have little if any effect upon the alinement of theremaining bushing holes adapted with the bushings of largereccentricity, and as a practical matter is taken care of by probabilityfactors unless the eccentricity of the bushings employed in the locatorholes is inordinately large.

In view of the foregoing, it is to be noted that several locator methodsmay be employed for attaching plate 30 to member 51 in properly alinedposition and with proper alinement between the several fasteningopenings.

In the first method, four locator holes in two locator positions areemployed in the mating parts as indicated at 31, 39, 53 and 61 in FIGS.1 and 2, and locator bushings of very small eccentricity employed in thelocator holes, the magnitude of the eccentricity being determined asrecited hereinabove by the permissible tolerance in the location of thecenter lines of the second pair of locator holes with or without thepermissible part shift between the two parts being taken intoconsideration, the latter being a function of the character of theinterchangeable assembly. The remaining bushing holes are thenpositioned to somewhat larger tolerances and receive fastener bushingshaving fastening receiving bores of a correspondingly greatereccentricity.

The second locator method employs again four locator holes in twolocator positions, one pair of locator holes receiving locator bushingswith concentric bores located preferably in the dimensional referencelocator hole. As contrasted to the first method, the eccentricity of thelocator bushings utilized at the second set of locator holes will betwice that used in method one for similar tolerances on the location ofthe center lines of the second pair of locator holes. The use ofconcentric locator bushings in locator holes 31 and 53 prevents partshift, except that of an angular nature. Again, in the remaining bushingholes, fastener bushings of somewhat larger eccentricities are employed.

In a third method, four concentric locator bushings are utilized in twolocator hole positions which requires extremely close locator holelocation tolerances of some slight degree of looseness of fit betweenlocator bushing and locator hole or between-locator bushing and fasteneror some combination of these three factors. An alternate to the thirdmethod would utilize conventional fastening devices, locator pins, etc.,without busings in both locator hole positions in which case some degreeof looseness of fit would be necessary in the locator holes varying inaccordance with the tolerances to which the center lines of the holesmay be held. Again, in both cases, the remaining bushing holes utilizefastener bushings or relative larger eccentricity.

A fourth method utilizes two concentric locator bushings in one locatorhole position, this being the dimensional reference hole with no secondlocator position being employed and all the remaining bushing holesreceiving fastener bushings of relatively large eccentricity as inprevious methods. In this method, more angular part shift is possibleand in certain cases this may be desirable for adjustment. Again, analternate method would be to utilize a conventional fastener, locatorpin, etc., in a single locator hole position rather than a concentricbushing. Or course, all other fastener openings would be positioned tosomewhat larger tolerances and receive fastener bushings of greatereccentricity as before. Close center line hole locational tolerances forlocator position number two are avoided using this method since nosecond locator position is employed.

It can be shown by diagrammatic load analysis that when eccentricfastener bushings are employed, and primarily where there is aconsiderable amount of eccentricity, there can occur a rotationaltendency in the bushings when they are subjected to loading. On a prac'tical basis this matter is controlled by a close fit of the fastenerbushings in their holes and also by the friction engendered in thebushings and the mating parts particularly when the fastener is pulleddown tight. In applications where large loads are encountered andfailsafe methods are utilized extensively, however, the use ofconcentric or minutely eccentric locator bushings in the locator holesprecludes the possibility of part shift under load even though thefasteners have not been pulled down as tight as is desirable or ifundetected tolerance build-ups have allowed a loose fit of the eccentricfastener bushings in their holes. In this respect the concentric orminutely eccentric locator bushings provide for a sound structure wherehuman errors may have oc curred or vibration may have loosened thefastening members. The main point to consider in examining part shiftunder load is that the rate and direction of shift at each fastenerpoint must be the same in order for part shift to occur when amultiplicity of fasteners are employed. Although this possibility ishighly unlikely, it is not impossible, and accordingly, the use ofconcentric or minutely eccentric locator bushings in the fasteningsystem eliminate even this extremely small chance of part shift underloading due to the rotational tendency of the eccentric fastenerbushings.

A specific embodiment of the invention in fastening bushings of theanchor nut type is illustrated in FIGS. 4, 5, and 6 which may beemployed for instance, in fastener openings 36 and 58 of the closure 30and member 51, respectively. The counterbored fastener opening inclosure 30 receives a flanged fastener bushing 80 having an eccentricbore 81 which is bevelled or chamferred at 82 at its upper end forreception of the head of a countersunk bolt or other fastening member.An anchor 83 is suitably secured to the underside of the member 51around the opening 58, as by the rivets 84 and carries a concentric nutmember 85 having an external flange 86 at its upper end and a pair ofdiametrically opposed laterally extending tabs 87 received in oversizeopenings 88 provided in a pair of cars 89 depending from the anchor 83.The nut member 85 is thus securely connected to the anchor 83 but isfree to undergo limited vertical and lateral movement while being heldagainst more than a slight degree of rotation. A fastener bushing 90fits within the fastener opening 58 of the member 51 and carries on itslower end an external flange 91 confined between the flange 86 of thenut member 85 and the underside of the anchor 83. The fastener bushing90 is freely rotatable within the anchor 83 and is formed with aneccentric bore 92, the eccentricity of the bore 92 being indicated at93. The bore of the nut member 85 is screw-threaded, and is chamferredat 94 at its upper end to facilitate insertion of a bolt thereinto,providing lateral translation into alinement with eccentric bore 92 offastener bushing 99.

This fastener assembly is particularly useful in installations whereaccess is available to only one side of the assembly in that a tool 95having a relatively elongate tip 96 formed of rubber or some othersuitable resilient or elastic material may be employed for adjustingboth of the fastener bushings 89 and 90 from one side of the assembly.As shown in FIG. 4, the fastener bushing may be slipped onto the tip 96,and the tip lowered through the fastener opening 36 to the eccentricbore 92 of the fastening bushing 90, the bushing 80 being manuallyrotated on the tip 96, and the bushing being rotated by means offrictional engagement by the tip in order to bring the bores 81 and 92into alinement and simultaneuolsy position the bushing 80 in thefastener hole 36. Thereafter, the tool with its tip 96 is withdrawn anda bolt introduced through the now alined bores 81 and 92 into the nutmember 85. As the fastening member is tightened in the nut 85, therewill be no tendency for either the bushing 80 or the bushing 90 to shiftits position because the shank of the bolt will prevent such shifting.As is the case in all of the locator and fastener bushing discolsed anddescribed herein, the bushings themselves are desirably and preferablymade of relatively hard and strong material and receive bolts or otherfastening members also formed of relatively hard and strong material soas to provide a very strong joint. Of course, the outer peripheries ofthe locator and fastener bushings being somewhat larger than thefastening bolt or fastening member, the bearing loads transferred to theclosure 30 and member 51 are necessarily applied to a greater area,consequently further increasing the strength of the joint. It is to benoted that the adjacent ends of the bushings 8t) and 96 are spacedslightly apart and do not extend entirely to the mating surfaces of theclosure 30 and member 51 so that thickness tolerance variations in 30and 51 do not prevent their physical frictional contact, and ensuresadequate pull down. Further, as shown in FIG. 5, the nut member 85 maybe deformed, as illustrated at 97 in order to function as a self-lockingnut which resists loosening under vibration or loading conditions.

A modified form of the anchor nut fastener which may also be utilized infastener openings 36 and 58 of closure 30 and member 51 is shown inFIGS. 7, 8, and 9 of the drawings. The same fastener bushing 80 isreceived in the fastener opening 36, but the fastener bushing-nut forthe member 51 is made in one piece rather than two. The lower fastenerbushing-nut is formed with an upstanding cylindrical collar 98 which isreceived in the fastener opening 58 and carries an eccentric bore 99extending downwardly into a screw-threaded, dependent neck 100. Anexternal flange 101 intermediate the collar 98 and neck is confinedwithin an offset cage 162 suitably secured to the underside of themember 51 as by the rivets 103. A thin metal plate 104 overlies the cage102 and the flange 101 and is secured to the cage by folded-over ears105 for securing the lower fastener bushing in the cage prior to themounting of the cage on the member 51. The bores 81 and 99 are alined inthe same manner as that described for the form of the invention shown inFIG. 4, it being noted that both the upper and lower fastener bushingsare free to undergo unlimited rotation. It is further noted that whenthe fastener bolt or the fastening element is inserted in the bores 81and 99 and into the threaded portion 100, there will be no rotation oflower fastener bushing because it and the upper fastener bushing are ondifferent centers and thus hold each other against rotation as the boltor fastening member is tightened into position.

In FIGS. 10 and 11 is shown a suitable belt which may be utilized witheither the nut plate fastener bushing of FIG. 4 or that of FIG. 8. Thebolt carries the usual, partially screwthreaded shank 106 and has abevelled head 107 fully receivable in the conical portion 82 of thebushing 80, there being provided a polygonal socket 108 in the center ofthe head 167 for reception of a suitable rotating tool, in theparticular form shown, the conventional Allen wrench.

A concentric locator bushing assembly which may be employed in thelocator holes 31 and 53 and/or in the locator holes 39 and 61, is shownin FIGS. 12, 13, and 14. This concentric bushing assembly is identicalto that shown in FIGS. 7, 8 and 9 with the exception that the bore 81'of the upper locator bushing 80' is concentric with respect to thebushing, and the bore 99' of the lower locator bushing is alsoconcentric of the lower bushing. Otherwise, the concentric locatorbushing assembly of FIGS. 12, 13, and 14 is identical to that shown inFIGS. 7, 8 and 9, and the parts thereof have been identified by the samenumerals with a prime added. It should be noted, however, that it ispossible to make the concentric locator bushing slightly smaller thanits concentric counterpart making installation in the wrong hole lesslikely. There is one further important difference between the twobushings in that the flange 101 of the lower fastener bushing shown inFIG. 8 is circular so that the lower bushing may rotate freely, whereasthe flange 101' of the lower locator bushing of the concentricmodification is square or polygonal so as to hold the lower locatorbushing against rotation within the cage 102'. Since the bores 81' and99 are not eccentric and are axially alined, this polygonal flange isnecessary to hold the lower locator bushing against rotation as a boltor other fastener member is tightened thereinto.

In a similar fashion, and as illustrated in FEGS. l and 16, the fastenerbushing assembly illustrated in FIGS. 4, 5, and 6 may also be made ineither a concentric form or a very slightly eccentric form as indicatedat 1%. Otherwise, the locator bushing assembly of FIGS. 15 and 16 isidentical to that of FIGS. 4, 5, and 6 and the parts thereof have beenidentified by the same numerals with a prime added thereto. A veryimportant modification of the upper fastener bushing is shown in FIGS.17 and 18, this modification being of a low profile protruding head typein which there is no requirement for counterboring of the fastenerholes. The plate 30' is provided with a cylindrical fastener opening 37'which receives a fastener bushing 107' having an annular, outwardlyextending flange 188 on its upper end and being provided with aneccentric bore 109, the eccentricity being indicated at 110, terminatingat its upper end in a chamferred or bevelled portion 111 for countersunkreception of the head of a fastening member or bolt such as that shownin FIGS. and 11. As is the case with all of the fastener bushingsdisclosed, the bushing 107 is desirably or preferably made of relativelyhard material and is adapted for use with bolts or other fasteningelements also formed of hard, high strength material so as to provide ajoint assembly'of quite considerable strength due to the materials ofthe fastening member and the fastener bushing, as well as the increasedbearing area between the bushing 107 and the walls of the fasteneropening 37 of the member 30. While this fastener structure is notcompletely flush, it has a low profile and may be readily employed ininstallations not requiring a completely flush fastener. The ease offorming the cylindrical fastener opening 37' as contrasted to theforming of a counterbored fastener opening facilitates considerably theease of installation of the fastener bushing 1G7, and a low profilefastener assembly of considerable strength is provided. It is also animportant feature of this modification that the weight of the fastenerassembly is reduced considerably as compared to conventional highstrength fastening assemblies that are currently available.

When access to both sides of the joint is available, the fastenerbushing assembly may be modified as illustrated in FIGS. 19 through 21.This modification, as will be more fully explained, provides for anincrease in the strength of the joint without enlargement of thefastening element making up the joint. This further modificationinvolves an upper plate 112 having therein a fastener hole 113counterbored from its lower end, and a lower plate 114 having therein afastener hole 115 counterbored from its upper end. The upper fastenerbushing 116 with its annular external flange 117 on its lower end isreceived in the hole 113 and carries an externally screwthreaded neck118 extending upwardly above the plate 112 for reception of a lock nut119. The bushing 116 is formed with an eccentric, fastening receivingbore 120 which is bevelled at its upper end at 121 for countersunkreception of a fastening member or bolt 122 of the type shown in FIGS.10 and 11. There is also provided a pair of diametrically opposedscrewdriver notches 123 in the upper end of the fastener bushing 116 foradjusting rotation of the fastener bushing 116 when the lock nut 119 isloosened.

The lower bushing 124 along with its annular external flange 125 at itsupper end is received in the counterbore of the plate 114, the bushing124 having an eccentric bore 126 which is screwthreaded in its lowerportion for reception of the bolt or fastener 122. The lower fastenerbushing 124 projects downwardly from the lower plate 114 and isexternally screwthreaded to receive a lock nut 127 of the controlledtorque type. The nut 127 has a polygonal head 128 on its lower end and abreak-neck groove immediately above the head 128 to form a thin Wallannulus 129 immediately above the head 128. With this arrangement, afterthe fastener bushing 124 has been properly adjusted so as to aline itsbore 126 with the bore of the upper bushing, the lock nut 12'? istightened into position by a Wrench or other tool applied to the head128, torque being applied until the thin annular wall 129 shears ortwists in two, thereby precisely determinhig the torque under which thenut 127 is tightened and making certain that the nut is tightened to thedesired degree.

A somewhat similar arrangement is shown in FIGS. 22 through 24 the partsbeing identical except that the conical counterbore 121 of the upperfastener bushing 116 is omitted, the structure is designed to receivethe machine bolt 130 rather than a countersunk bolt, and the lock nut127 is replaced by a lock nut 131 extending below the lower end of thelower fastener bushing 124 and carrying in its lower extremity atransverse shear pin 132 which may be engaged by a suitable tool fortightening the lock nut 131 into position. Again, the utilization of theshear pin 132 places an exact limitation upon the torque under which thenut 131 is tightened, the user tightening the nut on the lower bushinguntil the pin 132 either shears or twists out of the lower end of thenut 131, thus making certain that the lock nut is tightened to theproper degree but is not tightened excessively. The eccentricities ofthe forms of the fastener bushings shown in FIGS. 20 and 23 areindicated at 133 and 134 respectively.

It is known that in joints of the type herein disclosed,

the bearing loads across the shear joint are not uniform throughout thethicknesses of the plates being joined together but reach a peak at ornear the faying or mating surfaces of the joined parts. Thischaracteristic of this type of joint is fully discussed in AircraftStructures, Peery, McGraw-Hill, first impression, second edition, 1950,pages 303-306. I

The forms of the fastener assemblies illustrated in FIGS. 20 and 23 makeprovision for this concentration of bearing stresses that are near themating faces of the plates 112 and 114 by positioning the portions ofthe fastener bushings having the greatest cross-sectional hearing areas,the flanges 117 and 125, at the faying or mating surfaces so that agreater diameter and cross-section of realtively hard metal or othermaterial is so positioned as to be able to withstand more eifectivelythese peak loading points. More importantly the flanges 117 and bearagainst increased areas of the counterbored openings 113 and 115 whichare usually relatively soft in comparison to the bushings and hence areenable to effectively reduce the bearing stress in the plates 112 and114. By these structures, relatively small diameter high 1 1 strengthfastening members or bolts may be employed to provide a very strongjoint of reduced weight and great resistance to shear loadings. Ofcourse, each of these last described fastening assemblies may be readilyadjusted for aliuing of the bores of the bushings, after which thebushings are locked into place as described.

In FIGS. 25-27, there is shown an aircraft type stressed access door135, similar to the door 30 which covers an opening 136 surrounded bytwo beams 137 and two ribs 138 in a typical Wing section. This structureillustrates a typical use of the concentric locator bushings of FIGS. 14or 15, as well as the utilization of eccentric fastener bushings asillustrated in FIGS. 4- or 8. In such an assembly, access to the innersides of the fastening assemblies is not available, and accordingly,following any one of the several methods of installation previouslydescribed, a locator bushing is installed in one corner position 139 toestablish a first locator position and a dimensional reference position.This locator bushing would be of the concentric or the very slightlyeccentric type. Depending upon the method being employed, a concentric,slightly eccentric locator, or markedly eccentric fastener bushingassembly is installed at the diametrically opposite fastening position140, and fastener bushing assemblies of the greater degree ofeccentricity are installed at the remaining fastener hole locations.After the door 135 has been alined and locked into position by either orboth of the locator bushing assembly posit-ions 139 and 140, theindividual fastener bushings of the remaining assemblies are adjustedfor hole alinement and bolts of the type shown in FIGS. and 11introduced thereinto.

In all of the several methods and structures set forth herein, at leastone concentric or very slightly eccentric locator bushing assembly isemployed in a locator position, and after the two parts are lockedtogether in this manner, the remaining fastener bushing assemblies ofsomewhat greater ecentricity are alined and snugly secured.

Any of the various fastener bushings shown herein may be formed withconcentric or slightly eccentric fasteningreceiving bores so as toconstitute locator bushings, or may be formed with greatereccentricities, as also shown.

As employed herein and in the claims appended hereto locator bushingsmeans concentric bushing assemblies examples of which are shown anddescribed, as well as bushing assemblies having an eccentricitycompatible with and functioning within the limits of the permissiblepart shift between the parts. Thus, if the permissible part shift is0.010 inch for a two part assembly, the locator bushings may have aneccentricity of 0.005 inch or less and if a part shift of 0.006 inch ispermissible, the bushings may have an ecentricity of 0.003 inch or less.The tolerances for positioning the locator holes would followautomatically from the ecentricity of the locator bushings.

It is pointed out that any of the fastening nuts which receive the boltsor other fastening members may be of any of the numerous self-lockingtypes but are not necessarily self-locking in structure sinceconventional nuts may also be employed. This applies, of course, towhichever of the bushing assemblies functions as a nut. In addition, anyor all of the several forms of bushings described may have a light forcefit in a small portion of the bushing so that as the assemblies aretightened down in final position there will be additional frictionalengagement holding the bushings against any tendency to rotate orrevolve and to require readjustment frequently. (See FIG. 8.) In allinstances, of course, where one or two locator openings are located veryaccurately and employ one or more concentric bushings or bushings withvery slight eccentricity, or in other words locator bushings, the partsare locked together in the specified location, and this prevents partshift, and ensures and maintains complete interchangeability of parts.Specifically, the locator holes may be and preferably are of differentsize from the remain- 12 ing bushing holes if only for purposes of readyidentification.

In most instances, the mating fastener bushings will be of the sameeccentricity but in some cases it may be desirable to have mating oralining fastener bushings of differing eccentricity such as a locationin which a considerable degree of adjustment is desired, but one of themating parts might be able, because of available space or other reasons,to handle only a bushing of relatively small eccentricity. In such acase, the mating fastener bushing could be provided with a greaterdegree of eccentricity since the amount of adjustment or deviation isdetermined by the sum of the eccentricities of the two bushings. Thereare also other instances in which such pairs of fastener bushings ofdiffering ecentrieites may be desired or preferable.

The foregoing description of the invention is explanatory thereof andvarious changes in the size, shape and materials, as well as in thedetails of the illustrated construction may be made, within the scope ofthe appended claims, without departing from the spirit of the invention.

What I claim and desire to secure by Letters Patent is:

1. A locator bushing assembly for a blind fastener for joining togethertwo parts including a first locator bushing having an annular externalflange having a continuous annular face engaging in its entirety one ofthe parts and an eccentric fastening receiving bore, and a secondlocator bushing for mating with the first bushing, said second locatorbushing having an annular flange for engaging the other of the parts,the annular flange of the second locator bushing having a continuousannular face engaging in its entirety the other part, said secondlocator bushing being in the form of an anchor nut having a fasteningreceiving bore of an eccentricity different from that of the fasteningreceiving bore of the first bushing, and means for anchoring the secondlocator bushing to the other of the said parts, the second bushing beingrotatable about its axis with respect to said latter part whilemaintaining its flange in engagement with said latter part.

2. A locator bushing assembly as set forth in claim 1 wherein the firstand second locator bushings comprise a first set of locator bushings,and a second set of locator bushings comprising third and fourth locatorbushings having fastening receiving bores of eccentricities differingfrom one another.

3. A locator bushing assembly as set forth in claim 1 wherein the firstand second locator bushings comprise a first set of locator bushings,and a second set of locator bushings comprise third and fourth locatorbushings having fastening receiving bores of the first and secondlocator bushings and of eccentricity differing from one another and fromthe eccentricities of the bores of the first and second bushings.

4. A locator bushing assembly as set forth in claim 1, an anchor platesecuring the second bushing to other of said parts permitting freerotation of the second bushing with respect to said other of the parts,and an anchor nut anchoring the second bushing in the anchor plate andmounted for limited lateral movement in any direction.

5. A locator bushing assembly for a blind fastener for joining togethertwo parts including a first locator bushing having an annular externalflange having a continuous annular face engaging in its entirety one ofthe parts and an eccentric fastening receiving borepand a second locatorbushing for mating with the first bushing, said second locator bushinghaving an annular flange for engaging the other of the parts, theannular flange of the second locator bushing having a continous annularface engaging in its entirety the other part, said second locatorbushing being in the form of an anchor nut having a fastening receivingbore of an eccentricity different from that of the fastening receivingbore of the first bushing, and means for anchoring the second locatorbushing to the other of the said parts, the second bushing beingrotatable about its axis with respect to said latter part whilemaintaining its flange in engagement with said latter part, the firstand second locator bushings comprising a first set of locator bushings,and a second set of locator bushings comprising first and second locatorbushings having fastening receiving bores of eccentricities differingfrom the eccentricities of the bores of the first and second bushings.

6. A locator bushing assembly for a blind fastener for joining togethertwo parts including a first locator bushing having an annular externalflange having a continuous annular face engaging in its entirely one ofthe parts 10 and an eccentric fastening receiving bore, and a secondlocator bushing for mating with the first bushing, said second locatorbushing having an annular flange for engaging the other of the parts,the annular flange of the second locator bushing having a continuousannular face engaging in its entirety the other part, said secondlocator bushing being in the form of an anchor nut having an eccentricfastening receiving bore, and means for anchoring the second locatorbushing to the other of the said parts, the second bushing beingrotatable about its axis with respect to said latter part Whilemaintaining ts flange in engagement with said latter part, the first andsecond locator bushings 14 comprising a first set of locator bushings,and a second set of locator bushings comprising third and fourth locatorbushings having fastening receiving bores of eccentricities differingfrom the eccentn'cities of the bores of the first and second bushings.

References Cited UNITED STATES PATENTS 1,213,599 1/1917 Dow.

2,853,112 9/1958 Poupitch 1519 2,907,418 10/1959 Hudson et a1 14141.763,066,443 10/1961 Siler 851 3,041,913 7/1962 Liska 85-1 3,077,960 2/1963Lang 287-18936 3,123,120 3/1964 Grimm et al. 15141.7

FOREIGN PATENTS 570,661 2/1959 Canada.

EDWARD C. ALLEN, Primary Examiner.

RICHARD W. COOKE, JR., Examiner.

1. A LOCATOR BUSHING ASSEMBLY FOR A BLIND FASTENER FOR JOINING TOGETHERTWO PARTS INCLUDING A FIRST LOCATOR BUSHING HAVING AN ANNULAR EXTERNALFLANGE HAVING A CONTINUOUS ANNULAR FACE ENGAGING IN ITS ENTIRETY ONE OFTHE PARTS AND AN ECCENTRIC FASTENING RECEIVING BORE, AND A SECONDLOCATOR BUSHING FOR MATING WITH THE FIRST BUSHING, SAID SECOND LOCATORBUSHING HAVING AN ANNULAR FLANGE FOR ENGAGING THE OTHER OF THE PARTS,THE ANNULAR FLANGE OF THE SECOND LOCATOR BUSHING HAVING A CONTINUOUSANNULAR FACE ENGAGING IN ITS ENTIRETY THE OTHER PART, SAID SECONDLOCATOR BUSHING BEING IN THE FORM OF AN ANCHOR NUT HAVING A FASTENINGRECEIVING BORE OF AN ECCENTRICITY DIFFERENT FROM THAT OF THE FASTENINGRECEIVING BORE OF THE FIRST BUSHING, AND MEANS FOR ANCHORING THE SECONDLOCATOR BUSHING TO THE OTHER OF THE SAID PARTS, THE SECOND BUSHING BEINGROTATABLE ABOUT ITS AXIS WITH RESPECT TO SAID LATTER PART WHILEMAINTAINING ITS FLANGE IN ENGAGEMENT WITH SAID LATTER PART.